How create realistic semi gloss paint shader?
Final:



Overview:

Material itself is pretty simple even without using complicated PBR (but you can try it of course - look for CynicatPro) but the devil lays in details which are Bumps in this case.

You should work on them, as they are different for different parts of the Tank. Also Roughness map would be a good idea. Some parts are shinier then others.

This setup is just Diffuse mixed with Glossy by Fresnel and with procedural Bump Map.

You can try to use texture for bumps, same goes with roughness map.